5 kilometers = 3.1 miles
10 kilometers = 6.2 miles
13.1 miles
26.2 miles
An ultramarathon is any race longer than a traditional marathon (26.2 miles).
Fartlek is a Swedish term meaning "speed play". It is a form of unstructured interval training, where the training run is interrupted by speed bursts. The run consists of slow parts and fast parts.